This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The aim of this study is to investigate two methods of simulating walking exercise in lunar (1/6-G) and Martian gravity (3/8-G) with regard to the influence on the cardiovascular system and the biomechanical characteristics of gait. Both methods have been used so far for different applications in order to simulate certain gravity conditions showing its advantages and disadvantages. This research will determine which method is better suited to simulate astronauts'activity in lunar and Martian gravity environments on Earth.